(Received 4 August 2008;accepted 4 September 2008;online 13 September 2008)

The title compound, [Ni(C2O4)(C10H8N2)]n, is isostructural with its MnII, FeII, CuII and ZnII analogues. Each NiII atom is chelated by two oxalate ligands and one 2,2′-bipyridine, forming a slightly distorted octa­hedral geometry. Oxlate acts as a bridge to link neighbouring pairs of NiII cations, forming a one-dimensional wave-like chain. The crystal showed partial inversion twinning.

The design of coordination compounds has attracted long-lasting research interest not only because of their appealing structural and topological novelty but also due to their unusual optical, electronic, magnetic and catalytic properties, and their further potential medical value derived from their antiviral properties and the inhibition of angiogenesis. To date, much of the work has been focused on coordination polymers with organic acid ligands (Hong et al. 1997; Eddaoudi et al. 2001; Liang et al. 2004; Shi et al.2005).

As shown in Fig. 1, the Ni(II) atom is chelated by two oxlates and one 2,2'-bipyridine, forming a slightly distorted octahedral geometry. Oxalate acts as a bridge to link neighboring pairs of Ni(II) cations, forming a one-dimensional wave-like chain (Fig. 2). The Ni—N and Ni—O bond lengths are in the ranges 2.239 (5)–2.243 (5) and 2.161 (4)–2.166 (4) Å, respectively.

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

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